[Drake] R4B Inj Cable

[Dan W. Dooley]

Thanks everyone for the suggestions on the interconnect cables and plugs.  I
had two cables which earlier lacking the longer centre pins had shorter
ones.  One was the antenna and the other was the injection cable.  I have
now replaced both cables and plugs.  For the cable I used a length of Belden
82108 (RG-59) which upon looking up on line spec sheets shows the
capacitance to be 16.5 pf/ft.  That should do the trick.  I also installed
longer pin connectors on both cables.  

I will need to adjust the injection trimmers.  I've got a couple of tubes to
be obtained and replaced and when I have the covers off for that task I will
do the adjustments.  There is a difference in power output depending on
which unit is doing the VFO control.  With the transmitter in control, on
20m CW I get almost 150 watts out (the transmitter has been converted to use
6146 PA tubes) and about 10 watts lower when the receiver is in control.  I
may not see it being equal even after touching up the adjustments but at
least they will be adjusted to optimal.

The RCA plugs I have been using are different from the typical audio style
and different in more ways than just the longer centre pin.  The audio
style, at least most I have encountered, have external connections for
wiring.  They're very much like the 1/4 inch phono plugs with the tabs
extending behind for connection to each wire conductor.  The plugs I have
are made more along the line of a UHF PL259 plug in that the cable centre
conductor runs inside the plug and is soldered to the inside of the pin.
The shield is spread and forms a funnel of sorts and wraps around the base
of the plug and can totally encircle it and be soldered directly to that
part which is the outer shield of the plug.  I have no idea where I got
those but I had a small number with the longer pin and more with the shorter
one.  Now the cables are all using the plugs with the longer pin which will
make better contact.

WB5TKA


Dan W. Dooley
  email: dan at dooleystreasurechest.com
  Dooley's Treasure Chest 



-----Original Message-----
From: drake-bounces at mailman.qth.net [mailto:drake-bounces at mailman.qth.net]
On Behalf Of GGLL
Sent: Friday, November 8, 2013 8:05 AM
To: drake at mailman.qth.net
Subject: Re: [Drake] R4B Inj Cable

Yes, it is a 93 ohms impedance cable; but I believe it was chosen due to the
lower capacitance per m. rather than characteristic impedance.
Also lower attenuation.

RG59 capacitance specification is between RG62 and RG58.

Take a look:

 > http://www.rfcafe.com/references/electrical/coax-chart.htm

Interesting difference is, if you search Google for RG-62 data sheets, the
oldest specifies 13.5 pF/m, and some newer ones 43 pF/m ¿....?


Regards
Guillermo - LU5WE.

El 08/11/13 10:00, t.izak escribió:
> Drake uses RG-62 which is 93 ohm I believe for the injection cable !
>
> 73
> Tom/k1tl...
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